This invention relates to a row crop guidance system for maintaining the alignment of a pull type forage harvester with the crop rows being harvested. More particularly, the invention relates to a sensing unit for such a guidance system which is simply mountable and retrofittable on commercially available harvester headers.
One type of commercially available pull type forage harvester which is used to harvest a variety of row crops such as corn, sorghum, sugar cane and the like includes a base unit and an attached header. The base unit/header combination is towed through a field with a tractor. In the harvesting mode, the harvester is positioned outboard of the tractor by operation of a hydraulic cylinder connected to the tongue of the harvester so that the towing tractor does not have to ride over the crop prior to harvesting. When harvesting, the operator must look behind himself frequently to maintain the alignment of the harvester with the crop rows being harvested. After initially aligning the tractor and harvester properly relative to the crop rows, alignment is usually maintained by steering the tractor. However, the requirement for the operator to look over his shoulder frequently at the harvester leads to operator fatigue. When not in use the harvester is also positionable behind the tractor for transport.
Headers for such harvesters are commonly available in two sizes. One size is designed to harvest row crops with a 76.2 cm (30 inch) row spacing and another size is designed to harvest rows with a 96.52 cm (38 inch) row spacing.